CVE-2026-90039 - NFSD: Guard admin state-revocation walks with NFSD_NET_UP

CVE-2026-90039 - NFSD: Guard admin state-revocation walks with NFSD_NET_UP

https://cvefeed.io/rssfeed/latest.atom / Wed, 09/16/2026 - 13:32
CVE ID :CVE-2026-90039
Published : Sept. 16, 2026, 10:33 a.m. | 34 minutes ago
Description :In the Linux kernel, the following vulnerability has been resolved: NFSD: Guard admin state-revocation walks with NFSD_NET_UP Writing to /proc/fs/nfsd/unlock_filesystem, or sending the NFSD_CMD_UNLOCK_FILESYSTEM or NFSD_CMD_UNLOCK_EXPORT netlink command, walks the NFSv4 client hash tables to revoke open state and cancel async COPY operations. All three handlers gate that walk on nn->nfsd_serv, but a listener added via portlist or netlink listener_set sets nn->nfsd_serv before any nfsd thread starts. nfsd_startup_net() has not yet allocated nn->conf_id_hashtbl, so the walkers dereference a NULL table. A local administrator with CAP_SYS_ADMIN can crash the kernel this way without ever starting the server. nn->nfsd_serv is set when the service is created, which precedes table allocation. NFSD_NET_UP instead brackets the window where the tables are live: set at the end of nfsd_startup_net() and cleared in nfsd_shutdown_net() after they are freed, both under nfsd_mutex. Gating the three unlock paths on NFSD_NET_UP fixes the startup-time NULL dereference while preserving the earlier post-shutdown use-after-free fix.
Severity: 0.0 | NA
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